Put simply government officials created a scheme to buy up a bunch of unused water rights, then use state and federal dollars to pay themselves incentives to continue not using the water.
I'm not sure if this is what they're talking about, but I've heard it said more than once that a lot of Utah politicians have conflicts of interest with respect to allowing more water to flow into the lake (ties to agriculture, etc). The situation has probably changed somewhat now that parts of the city have shelter in place orders because of toxic clouds, but people have been talking about it for decades now.
If the politicians said they wanted to buy up water rights and not use them. and actually bought them up so they can used by their cronies, that would certainly be grift, but OP seems to be against "hold[ing] water rights without developing them", which is exactly what you have to do if you want more water to flow into the lake...